title: Rosette-like structures in the spectrum of spitzoid tumors.
abstract: BACKGROUND
  Spitz nevi demonstrate a diverse spectrum of morphologies. Recently, there have been two reported examples of Spitz nevi with rosette-like structures similar to Homer-Wright rosettes. Rosettes have also been described in melanomas and in a proliferative nodule arising in a congenital nevus.
  
  
  METHODS
  A retrospective review of 104 cases of Spitz nevi and variants (n = 51), pigmented spindle cell nevi (n = 26), combined melanocytic nevi with features of Spitz (n = 8), atypical Spitz tumor (AST, n = 9), and spitzoid melanoma (n = 10).
  
  
  RESULTS
  Rosette-like structures were present in 3 of the 104 cases (2.9%), including a compound Spitz nevus, a desmoplastic Spitz nevus, and an AST. All three cases demonstrated several foci of small nests of epithelioid cells with peripherally palisaded nuclei arranged around a central area of fibrillar eosinophilic cytoplasm. Immunohistochemical staining of the three spitzoid lesions demonstrated that the rosette-like structures express S100 protein, Melan-A, and neuron specific enolase (NSE) and lacked expression of neurofilament, glial fibrillary acidic protein and synaptophysin.
  
  
  CONCLUSIONS
  While uncommon, rosette-like structures can occur as a focal feature in Spitz nevi and AST. Rosette-like structures may represent a normal morphologic finding in Spitz nevi, and awareness of them may prevent misdiagnosis as a neural tumor or melanoma.
authors.affiliation: Department of Pathology, University of Michigan, Ann Arbor, MI 48109, USA.
authors.forename: David P
authors.initials: DP
authors.lastname: Arps
authors.forename: Paul W
authors.initials: PW
authors.lastname: Harms
authors.forename: May P
authors.initials: MP
authors.lastname: Chan
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Fullen
mesh_terms: D000328:Adult; D002467:Cell Nucleus / Q000378:metabolism / Q000473:pathology; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008297:Male; D008545:Melanoma / Q000378:metabolism / Q000473:pathology; D009363:Neoplasm Proteins / Q000096:biosynthesis*; D018332:Nevus, Epithelioid and Spindle Cell / Q000378:metabolism / Q000473:pathology; D012189:Retrospective Studies; D012878:Skin Neoplasms / Q000378:metabolism / Q000473:pathology
chemical_list: D009363:Neoplasm Proteins
keywords: Spitz nevi; melanoma; rosette